Stratigraphy
stratigraphy, in geology, the study of rock layers, or strata, particularly their ages, compositions, and relationships to other rock layers. stratigraphy provides geologists with clues about the earth`s past. stratigraphy also allows geologists to predict what types of rocks lie below the ground and to understand geologic processes. consequently, most geologists regularly use basic elements of stratigraphy in their work.
Principles of stratigraphy
Stratigraphy relies on four simple principles
Stratigraphy relies on four simple principles to unveil geologic history. the principle of original horizontality states that the sediments that form sedimentary rocks are usually deposited in approximately horizontal sheets. this principle is invaluable for reconstructing the earth`s history because it allows geologists to distinguish between undisturbed and deformed rock layers. the term deformation generally refers to faults ( fractures where one side has moved relative to the other ) or folds that form in rocks, typically during mountain-building events. for example, rocks 250 million years old near the top of the grand canyon lie in horizontal sheets ; similar rocks near las vegas, nevada, are tilted on end. therefore, geologists infer that rock layers in the grand canyon have not been strongly deformed in the 250 million years since they were deposited. by contrast, the las vegas area has experienced strong deformation since that time.
